Radio location system



pl'i 27, E948. E. M. DELORAINE ETAL 2,440,250

RADIO LOCATION SYSTEM Filed June 5, 1943 2 Sheets-Sheet l PAM/wrm?- 25INVENTORS UMa/vo r1. @nona/ms E. M. DELORAINE ETAL 2,440,250

RADIO LOCATION SYSTEM K' Filed June 3, 1943 2 Sheets-Sheet 2 IN VEN TORSfano/vo M. naam/NE 'M/LE .m5/N Pnl/L E M. aLaEss BY Patcnted ipr. 27,i948 REO LGGTN SYS'EEM v Edmond M. Delce and Ee York, N. Y., and PaniFrancois Paris, France, assignors to Lapin, New Marie Gioess, HnationalStandard Electric Corporation, New York, N. Y., a corporation ofDelaware Application .ie 3, 1943, Serial No. 489,476

lin France April d, 194@ K 1 Claim.' (Ci. 25d-1.70)

The present invention refers to devices indicating successive positionsof moving bodies, and also to remote control systems for these movingbodies.

More particularly, one of the objects of the invention is to provideindicating devices for following from a central station on the groundthe displacements in space of a moving body, such as an airplane,provided with radioelectrlc communication means, either active, such asa transmitting-receiving station, for example, or passive, as, forexample, a reflecting system which further may be reduced to thereflecting surfaces of the airplane.

According to certain features of the invention, two radioelectric landstations located at given points far from each other emit periodicalradiations, for example trains of pulses, which are returned by themoving body, either by radioelectrc communication means of the usualtypes on board the moving body, or by reflecting means installed on themoving body or forming part of the moving body, the return radiationsbeing received by said land stations and applied to an indicating deviceat one of the stations or at a central post connected to the stations.

According to other features of the invention, the radiationsperiodically emitted by the land stations may be of differentwavelengths, the return radiations transmitted by the moving bodythemselves being of different wavelengths with respect to one anotherand preferably with respect to the former, in the case where the movingbody is provided with means for receiving and retransmitting theradiations of the land stations.

The invention also provides at each land station means for emitting adirected radiation periodically and means for finding the direction oi'the energy of this radiation that is reflected by the moving body, inthe case Where this moving body is not equipped with activeradioelectric means.

According to still other features of the invention, the signalsperiodically transmitted and received by the land stations are appliedto such an indicating device that it furnishes a precise, continuous orintermittent, indication of the geographical position of the moving bodyon a screen that also shows geographical locations of interest, such asthe land stations, or points that the moving body must pass or ily over.

According to other features of the invention, such` indicating devicesmay consist of an assembly of two cathode-ray oscillographs soassociated with a screen that the two luminous indications respectivelycontrolled by the signals may consist of an unsilvered mirror arrangedatl 45 between the uorescent faces of the cathoderay oscillographsarranged at either at one of the land stations or at a central postconnected to these stations. One or both particular indications on eachuorescent screen may be obtained, according to another feature of theinvention, by applying to the two pairs of deection electrodes of eachoscillograph such phaseand amplitudedeiiecting voltages that in theabsence of impressed signals the luminous spot will describe a spiral.The application to such an oscillograph of a signal such as a pulse orstill better a pair of pulses, for example to the control grid, owing tothe relative duration of the received signal with respect to the angularspeed at which the spiral is described will furnish a practicallycomplete circle on the fluorescent screen. 0n the common translucentscreen will be obtained therefore two circles, each centered about apoint corresponding to one of the land stations, Whose intersection willdefine the position ofthe moving body with respect to the land stations.

According to a still another feature of the invention, the position ofthe moving body can be watched with variable precision by causing thedefinition of the screen scanning diagram to vary, which results in amodification, enlargement or reduction, of the geographical area underwatch.

The invention will be explained in detail in the following description,-given with reference to the accompanying drawings, in which:

Fig. 1` shows schematically a system for watching and guiding `movingbodies, in accordance with features of the invention;

Fig. 2 shows an indicating-device screen corresponding to the systemshown in Fig. 1;

Fig. 3 shows the screen of a cathode-ray oscillograph, upon which appearthe indications used in the present invention; K

Figs. 4 and 5-show schematically two embodiments of a system forwatching and guiding moving bodies, incorporating features of theinvention; and

Fig. 6 shows the screen of a cathode-ray oscillograph whose scanning hasbeen modified so as to obtain an enlargement of the displacement zone ofthe moving body.

In. Fig, 1 are shown at A and B two watch staselves, A or B.

The problem consists in reproducing'upon-the screen of an indicatingdevice such as-E (Fig. 2).`

teni-:iny accordance with the relative position A', B', P' of stationsA.'

and B and of moving body P, hence in solving triangle ABP in graphic andautomatic'fashion.'

When moving body P is in active communication with stations A and B orone of the stations only, it is possible, moreover, to obtain additionalindications transmitted by the moving body, it being possible likewiseto convert thesey radio indications into visual indications ii desired.

Where only one station A or B is available, it will be necessary toreproduce upon the screen of an indicating device the relative positionsof that station end of moving body P, so as to obtain a doubleindication on that station, while when two xed stations are available asingle indication will suice at each station. In other words, where twostations A and B cooperate with the moving body it will suffice todetermine either the distance or the bearing of the moving body withrespect to each station, while when only one station cooperates With themoving body it will be necessary to obtain simultaneously an indicationas to the distance and an indication as to the bearing of the movingbody. in Fig. 2 the actual position of point P will be determined by thelocations of three points A', B', and P', by means of squared scaled Q,while in Fig. 3, which represents the case involving only one ilxedstation, the position of the moving body will be determined by thedistance A"P" and the angle c or the straight line A"P" with an axis oforigin of angles A" X.

To obtain such a result, the invention provides particularly the use ofa particular scanning o a luminous-indication oscillograph, such as acathode-ray oscillograph. Such a spiral scany ning, indicated by adotted line et s in Fig. s,

can be obtained by applying to the two pairs Aof deiiecting elements ofthe cathode-ray oscillograph sinusoidal voltages suitably shifted lnphase and the amplitude of which varies slowly. This may be done, forinstance, in the manner shown in the United States Patent No. 1,706,185.The law of variation of these sinuosoidal voltages is so adjusted thatthe radius of the spiral at each point varies proportionately to thedistance that would be covered by the moving body if it werej displacedin a straight line at a constant speed. The reception at the centralstation of a signal coming from a iixed station and corresponding to anindication about the distance or the bearing of the moving body causesthe ap.. plication of a grid voltage of the cathode-ray oscillograph,the normal grid voltage being such that no trace will appear upon theluminescent screen of the said oscillograph. The resultant indication isa practically complete luminous circle owing to the relative 'durationof the received signal with respect to the angular speed at which thespiral is described.

By providing another oscillograph similarly controlled from anotherfixed station, 'another luminous circle will be obtained also on thescreen of this latter oscillograph. By superlmposing the twoindications, the intersection of these two circles will indicate themoving body under observation.

Such an indicating device is therefore of par.. ticularly advantageoususe with a watching sysanother aspect of the invention, such as shown inFig. 1. Various arrangements relativef to this watching system andincorporating features .of the invention will now be described.v

Stations A andB each comprise 'a radioelectric transmitter i, 2 and a.lradioelectric receiver 3, 4,

shownin Fig. 4. Transmitterv 1 of Watch station Aemits short periodicalpulsesv on carrier frequency fi and transmitter 2 cf watch `station' Bon carrier1 frequency'f.vr Preferably. but not necessarily, thetransmission is eiected'on ultrashort wavelengths, metrical ordecimetrical wavelengths, for example.

The signals coming fromtransmtters 'i and 2 are received by'moving-bodyP, shownin the form of an airplane in Fig. li. This moving body isprovided with either active or passive radio.- electric means forreturning thev signals in harmony with the emissions from A and B., lItmay. for example, bel provided with two receivers tuned to frequencies.ft and f2 andwthv two transmitters automatically or otherwiseretransmitting emissions fi and f2, either on the same frequencies or ondierent frequencies f3' and ffl. Or still, the movingbody maybe-provided with two reecting antennas tuned to frequencies fi and f2that will return the emissions by reilection. When the moving body doesnot cooperate voluntarily with stations A and B, a portion of theemissions from transmitters i andA Zwill be re'- two cathode-rayoscillographs 1 and 8, after having been suitably retarded in articialretardation lines 9 and I il.

The control of the scanning of each oscillo-j graph is accomplished inthe manner described above for obtaining a spiral scanning, of thescreen. For this purpose a pulse generator H, y

installed at central station C, for example, simultaneously supplies thepulses sent out by transmitters i and 2, located at stations A and B, asindicated by cables l2 and I3, and synchronizes the spiral deectionvoltages 4applied to the respective deflection plates of cathode-rayoscillographs 1 and 8, over suitable retardation lines Il and l5 andscanning-voltage generating circuits IB and I1. Because of thesynchronization of the scanning voltages with the pulse generator Il,each spiral starts from the center a predetermined time determined bythe retardation lines |'4 and I5 after the pulse is transmitted.

These various circuit members, retardation lines, scanningvoltagegenerators, and pulse transmitters and receivers may be of any suitabletypes and hence will not be described in greater detail, being known inthemselves.

Through the combination of spiral scannings and of pulses applied to thecontrol grids of the oscillographs, and thanks to thesynchronizedcontrol method just described, two circular indications 20and 2| rare obtained on the oscillograph screens I8 and I9. The diameterof each circle 20 and 2| corresponds, respectively to the distance ofthe moving body P from each station A and B. By simultaneously observingthese two luminous indications 20 and 2|, for example by will see onscreen 22 an image similar to that shown in Fig. 2. The coordinates ofpoint P' can then be read on squared scale Q.

Retardation lines t, i@ and it, l5, are adjusted so as to take intoaccount the constant time delay in the equipment on moving-body P and inreceivers 3 and 5 and the transit time from each` station A and B tocentral station C. in order to refer the pulse arrivai time to a commontime origin.

Line 2d indicates a control line for receivers 3 and 4, which may beused for sensitivity-control circuits for the receivers.

In the embodiment lust described, the coordinates of moving body Pmeasured with respect to station A and B were the distances AP and PB.However the measured coordinates of moving body P maybe the distancetwice the distance AP and the length equal to the sum of distances APplus PB.

For this purpose, only one radioelectric transmitter transmittingtowards the moving lbody need rbe used. This transmitter, located at A,for example, is to transmit on a carrier frequency f, as before, shortperiodical pulses at predetermined time intervals for aperiod of timesuiicient to make a measurement. These pulses will be received bymoving-body P, whence they will be returned, either simply by means ofan an-y tenna tuned to frequency f, or after amplification on frequencyf by a relay, or after a change in frequency or detection and newmodulation on another frequency f'. moving body may further be effectedautomatically by arranging a device on board theA moving body so that itwill be released either by the signal coming from the transmitterlocated'at. A or/ else at a predetermined instant by means of clockwork.

Two r'ceivers located respectively at A and B receive the pulses sentback by P and transmit them'to a central station C. At central station Cthe time of arrival of the pulses coming from A may be compared withthose coming from B, that is, the pulses that have followed path AP-i-PAwith those that have Lfollowed path AP-l-PB. This comparison may be madein the mannerdescribed with regard to Fig. 4.

.In the two examples just described it is obvious that central station Cmay, in practice, be located either at station A or B, but preferable atstation A in the second case. The BC or BA connection may be made eitherby cable or by radio.

When only A transmits, a device may be arranged at B of the same natureas thel one installed on the moving body, so that it will receive onfrequency f or f transmitted from moving-body P and retransmit onfrequency f or f or on a. third frequency f". While it is possible touse at B and P amplifier relays with a single frequency f, precautionsbeing taken at each point tofavoid any confusion between thetransmissions from the other two points, nevertheless itis preferable touse three different frequencies, which leads to the employment at B andP of The re-radiation by the.

high emciency pulse-transmitters without additional precautions.

. When only one xed station is available or it Y.

- shown in Fig. 5, in harmony with the picture of the coordinates of themoving body given in Fig. 3.

In Fig. 5, which shows schematically the equipment required at a fixedstation in order to follow the route of a moving body P, such as anairplane, a radioelectric transmitter 25, preferably operating on ashort or ultra-short wavelength, sends out periodical pulse trains,which are returned by the moving body either by means of an antennatuned to the same wavelength,V or to another wavelength, or else by thereflection procucefd by the metallic masses of the moving body i sel Atthe same time that the pulses are sent out by the transmitter, they areapplied in the manner indicated before to the deflection-plates of acathode-ray oscillograph 26 so as to synchronize a spiral scanning ofthe screen 2'! of this oscillograph obtained by means of ascanningvoltage generator 28. The pulses sent back by the moving bodyare received by a radio direction nder 29 associated with a pulsereceiver 30.

`Alfter having been retarded in a suitable retardation line 3i, thepulses received by receiver 39 are applied to the control grid ofcathode-ray oscillograph 26, thus causing the appearance of a circularindication such as indicated at 32 in Figs.

5 and 3.

The output voltages of radio direction ilnder 2.9 are applied in knownmanner over a retardation line 33 to the two pairs of deflection platesof a cathode-ray oscillograph 34 in order to cause the appearance on thescreen 35 of this oscillograph of a rectilinear indication, radius ordiameter, giving the bearing of moving-body P with respect to a givenorigin. Such an indication is found again at A"P" in Fig.` 3.. Byobserving the two indications 32 and 36 simultaneously, by means of atranslucid screen 3l, for example, an observer 38 will see the imageshown in Fig. 3 and will be able to deduce therefrom the bearing and thedistance of the moving body being watched.

It should be remarked that the distance "AP" actually represents twicethe distance from the moving body to the watch station; in fact, asshown by impulse indications 39 to M below screen Ein Fig. 3,transmission pulse 3-9 of transmitter 2.5 Vcorresponds to the center ofthe diagram, pulse 40 indicates the time the pulse is received at themoving body and occurs halfway between the center of the diagram andcircular indication 32, while the third pulse 4I is the return of thereflected pulse received at 30. The distance-scale hence should bechosen as to allow direct reading.

When it is desired to follow the moving body more accurately, forexample when the moving body has reached an interesting position inspace, an enlarged image of its route can be obtained, according tostill another aspect of the invention, by acting upon the scanning ofthe cathoderay oscillograph or oscillographs. Fig. 6 shows at' 42 suchan enlarged scanning where two successive positions of the moving bodyI3 and 44 are given by the intersection of pairs of luminous accontocircles d3 and do' in the case of Fig. 4. The enlargement of the spiralscanning can 'be obtained either by extending uniformly the coordinatesof the initial diagram through increase of the amplitude of the deectionvoltages, then bringing the interesting portion baci; again on thescreen oi the oscillograph by means of appropriate adjustable biasingvoltages applied to the deiiection system of the oscillograph, or bycausing the scanning speed to vary so as to show an enlarged portion ofthe diagram in the interesting region by acting upon the circuitdetermining the law of variation of amplitude of the deilectionvoltages, or still by using a device having a scale and vernier similarto those described in application Serial No. 417,180, ied October 30,194i.

Still other modifications and adaptations of the arrangement shown anddescribed may be made without departing from the scope of the invention.

What is claimed is:

A system for indicating the position of a distant body capable ofreturning received radio frequency impulses, comprising means forradiaing energy impulses to said body, a rst receiving means forreceiving impulses returned from said body, a second receiving means forreceiving impulses returned from said body. said second receiving meansbeing spaced a predetermined significant distance from said firstreceiving means, said body having diierent characteristics of positionwith respect to said first and said second receiving means respectively,a rst reproducing means responsive to the impulse received by said iirstreceiving means :for producing the rst indication corresponding to acharacteristic of the position of said object with respect to said iirstreceiving means, a second reproducing means responsive to the impulsereceived by said second receiving means for producing the secondindication corresponding to a characteristic of position of said bodywith respect to said second receiving means, and means for combiningsaid indications including means to superpose the separate indicationsthereby producing a resultant indication of the position of said bodynot given by the said first and second indications when uncombined. saidcombined indications being positioned with respect to each other inproportion to the spacing of said`rst and second receiving means.

EDMOND M. DELORAINE.

LABIN.

PAUL FRANGOES MARIE GLOESS.

REFERENCES CITED The following references are of record in the ille ofthis patent:

UNITED STATES PATENTS Number Name Date 2,207,267 Plaistow@ July 9, 19402,083,203 Schlesinger June 8, 193'7 1,706,185 Sabbah Mar. 19, 19292,251,984 Cleaver et a1 Aug. 12, 194i 2,225,046 Hunter Dec. 17, 19402,055,883 Terry Sept. 29, 1936 2,301,826 Steudel et al Nov. 10, 1942FORElGN PATENTS Number Country Date 526,658 Great Britain Sept. 23, 1940

